Steinberg WaveLab 3 Operation Manual
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WAVELAB Off-line processing 9 – 191 Fade-in and fade-out A fade-in is a gradual increase in level and a fade-out is of course the op- posite. There are two ways of applying fades in WaveLab: by using the Easy Fade function or by using the Fade dialog. Easy Fades The Easy Fade function allows you to very quickly apply a fade-in or fade- out to an audio file, without having to make any settings: 1.To create a fade-in, make a selection from the start of the audio file to where you want the fade-in to end. Similarly, to create a fade-out, you should make a selection from the position where you want the fade to start, to the end of the audio file. 2.Select “Easy Fade” from the Process menu, or press [Ctrl]-[D]. A fade is applied to the selection. The shape of the fade is governed by the Default fade/ crossfade setting in the Preferences–Wave edit tab. Using the Fade dialog The Fade dialog allows you to specify the desired shape of the fade, and to create fade-ins or fade-outs anywhere in a file: 1.Make a selection that spans from where you want the fade to start to where you want it to end. 2.Select fade-in/out from the Process menu to open the Fade dialog. 3.Use the Type options to select a fade-in or a fade-out. 4.Set the Offset and Damping parameters. A graph in the waveform indicates the resulting shape. The Damping value indicates how much the wave will be attenuated at the Offset point. A 6dB Damping with a 50% Offset normally gives the most natural results. See “Crossfade” below for more details.
WAVELAB 9 – 192 Off-line processing Crossfade A crossfade is a gradual fade between two sounds, where one is faded in and the other faded out. This function allows you to do just that. It also lets you create plain mixes of two sounds. Performing a regular crossfade The material you want to crossfade can either be in two different sections of the same file, or it can be in two different files. Since the crossfade is a type of paste operation, you must start by getting the section into which you want to fade (the later part of the fade) onto the clipboard. 1.Select the section into which you want to fade. 2.Select Copy, from the Edit menu. Now it’s time to move over to the section from which you want to fade, which might very well be in another Wave window: 3.Select the section from which you want to fade-out. This selection cannot be longer than the selection you just copied, or the program will not be able to perform the crossfade! The length of this selection will determine the length of the actual cross- fade (check the length on the status bar). In a typical case, this selection will be at the end of the wave. See below for details. 4.Select Crossfade from the Process menu. The dialog appears and crossfade slope indicators are shown in the current selection. 5.Make sure that “Mix without fading” is not activated in either section.
WAVELAB Off-line processing 9 – 193 6.Adjust the Offset and Damping parameters as desired. The shape of the two curves is indicated in the selection. See below for details. 7.Click the Paste button. Please note that if both waves already have full level sections in the cross- fade area (for example if you have normalized both waves), clipping (and hence distortion) might occur! If this happens, reduce the amplitude of both waves by 3 to 6 dB and try again. Also note however, that if one of the “Inverse of Fade In/Out” boxes is checked, clipping can never occur. How the fade is done • As described above, the length of the fade is determined by the size of the selec- tion in the file into which you paste. • The pasted material has to be longer than the selection you paste “into” (or there won’t be enough material to finish the fade). • Any “excess” material in the copied selection will appear after the fade (at “full level”). The wave is lengthened as needed. • Any material that originally appeared after the selection in the file into which you paste, will be moved so that it now appears after the newly pasted material. About the curves The design of the fade and crossfade curves is based on psycho-acous- tic research material, in order to give as pleasant and harmonic a result as possible. For each of the two sections – the fade-out and the fade-in – you can se- lect an Offset and a Damping value. When you adjust these values, the curves in the wave are adjusted accordingly so that you can see what kind of crossfade you will get. The Offset factor determines where in the fade section the file will play at its “mid level” (normally half the level, see below).
WAVELAB 9 – 194 Off-line processing The Damping parameters adjust the “steepness” of the fade. For example, a -6dB setting for the fade-in will result in a normal fade, where the level is half the original when it reaches the Offset point. Values closer to 0dB will emphasize the beginning of the fade-in wave. Values closer to -18dB will make the fade-in sound drop drastically at the beginning of the fade. Here, the default -6dB Damping curves with 50% Offsets are selected. This gives you a normal crossfade with the focus on the middle of the fade. In this example, the Offsets have been moved so that the focus of the fade is more to the left. This means the fade-out is faster than the fade-in. However, both Damping factors are still set to the standard -6dB. Mix without fading If you activate “Mix without fading” for either section, it will play at full level throughout the entire fade. An example Let’s say you have two environmental sound effects you want to fade be- tween, “city” and “restaurant”. You want to fade from “city” to “restau- rant”. The two sounds are in different windows. 1.Select the entire “restaurant” wave and copy it. 2.Make a selection in the “city” wave, from a point close to the end. The length of this selection is equal to the length of the fade. 3.Open the crossfade dialog, set both Offsets to 50%, both Damping set- tings to -6dB, deactivate both “Mix without fading” options and click the Paste button. The “city” wave is now lengthened, so that it starts as it originally did, then fades over to the beginning of the “restaurant” wave and ends like the “restaurant” wave.
WAVELAB Off-line processing 9 – 195 Invert Phase This turns the signal “upside down”, which is the same as inverting the phase by 180°. No settings are needed for the operation. There is no audible change when you invert the phase of a mono signal. However, if one channel in a stereo pair is out of phase with the other, this will lead to artifacts such as a drop in the bass register and a “blurred” stereo image. The most common use for this function is therefore to fix a stereo record- ing where one of the channels has accidentally been recorded out of phase with the other. Reverse This function reverses the selection, as if playing a tape backwards. No settings are needed. Eliminate DC Offset This function removes a problem that most often appears due to mis- matches between various types of recording equipment. This function should be applied to whole files, since the problem is normally present throughout the entire recording. A DC offset is when there is too large a DC (direct current) component in the signal. If the DC offset is really bad, it can be visible as the signal not being visually centered around the “zero level axis”. However, the DC off- set can be significant without actually being seen. A wave with a serious DC offset A DC offset is problematic for two reasons:
WAVELAB 9 – 196 Off-line processing • It affects where the zero crossings appear, which in turn affects the smoothness of splices between audio files. • Certain processing options do not give optimal results when performed on files with a DC offset. Checking for and eliminating DC Offset 1.Select the wave you want to check and fix. 2.Select “Eliminate DC Offset” from the Process menu. A dialog appears stating the amount of DC offset. 3.Click OK or Cancel. Waveform Restorer This lets you remove intermittent clicks and pops in an audio file. First make a selection encompassing the artefact you want to remove, then ap- ply one of the available methods. Usually, you will have to use a high zoom factor to be able to locate and select the undesired element. The Waveform Restorer lets you select one of several available restora- tion methods. The selected method is described in the dialog. • Note that if you want a more direct control of the process, you can instead use the Audio error detection and correction dialog for a more “hands on” way of restoring audio files. See “Audio error detection and correction ” on page 631. Time Stretch Time stretch is an operation that allows you to change the length of a re- cording without affecting its pitch. Actually the standard term “time stretch” is a bit misleading since you can of course also make the material shorter. This function is most often used to make a section of audio fit in with some other material. Therefore this dialog is set up exactly for that. You select the material to be stretched and use the options in the dialog to find a stretch factor (the “Percentage”). This is done by specifying the desired length, or the desired tempo, all according to what the situation requires.
WAVELAB Off-line processing 9 – 197 Opening the dialog When you open the dialog, the following information about the selection is displayed: Specifying a percentage directly If you know by how many percent you want to change the length, you can enter this value in the “Percentage” field. Calculating the percentage by specifying a new length •If you know the desired length in samples, adjust the Samples value in the “Desired result” section. •If you know the desired length in minutes, seconds and milliseconds, ad- just the corresponding value in the “Desired result” section. Regardless of which you choose, the other values and the Ratio are updated accordingly. The original length in seconds. The original length in samples. The calculated original tempo according to the set length and time signature.
WAVELAB 9 – 198 Off-line processing Calculating the ratio by specifying a time code range If you want to fit the selection to a certain range, for example in a video or film sequence, you can specify the start and end of this range as time code values: The other values and the Percentage are updated accordingly. Calculating the Percentage by specifying a new tempo If you know you want the selection to play back in a certain tempo, after the stretch, proceed as follows: 1.If you know the current tempo of the selection, type it in the Tempo field in the Source part of the dialog. 2.If you don’t know the exact current tempo, but the length of the selection and the time signature, you can specify these instead, in the Bars and sig- nature fields, and the Source tempo will be calculated for you. Please note for these operations to work properly, the exact specified source tempo or length must be selected. Any deviation from the real values will be transferred to the stretched audio. 3.Type in the desired tempo in the Tempo field in the “Desired result” section. Reset The Reset button resets the Percentage to “100%”. Enter the desired end position here. Enter the start position here.
WAVELAB Off-line processing 9 – 199 Additional settings Limitations Time stretch is a very complicated Digital Signal Processing (DSP) oper- ation. It requires complicated mathematical operations and always affects the sound quality to some extent: • For speech, stretch factors within a ±30% limit will normally provide very good re- sults. • For composite music, try to limit the range to ±10%. • For sensitive material, like solo piano, try not to exceed ±3%. • Note that if the DIRAC algorithm is used (see below), the above range rec- ommendations can be extended and still produce very good results. Setting Description Quality There are three Quality settings, “Quick Process”, “Standard” and “High Quality”. The High Quality mode provides very high quality pitch correc- tion, but the process will take longer. For most uses, the Standard mode is probably sufficient. Use DIRAC processorThis is described separately below. Preserve pitch When this option is activated, the pitch of the audio material will not be affected when you apply Time stretch. This is the normal mode of oper- ation. If you turn this off, the pitch will change proportionally with the Time stretch ratio, much like when speeding up or slowing down a tape recorder. Audio quantize When this option is activated, the length of the resulting file will be exactly the one displayed in the “Desired result” section of the dialog. When it is deactivated, the actual file length may differ by a few milliseconds. If you don’t need this accuracy, you should leave the option deactivated, for a slightly better audio quality. Rhythm accuracy This is only available if “Standard” or “High Quality” mode is selected. Set this parameter according to whether the rhythmic feel of the audio material has a high priority or not. If you set this to a high value, the tim- ing and rhythmic feel will be preserved as far as possible, which is im- portant for drum tracks, etc. If you set it to a low value, the audio quality can be slightly better, but sections of audio might be moved slightly (in the milliseconds region) in the process.
WAVELAB 9 – 200 Off-line processing About the DIRAC processor The DIRAC (DIRAC Time Stretch/Pitch Shift technology, ©2005 Stephan M. Bernsee) engine is a very high quality time stretcher, perhaps the best available on the market today. It will produce the best quality re- sults possible, but the trade-off is longer processing times. In WaveLab, you can use the DIRAC algorithm to process mono or stereo files with up to 96 kHz sample rates. • If you check the “Use DIRAC processor” box there will be an extra quality mode available (“Best (very slow)”) and 6 processing options available on the pop-up menu. • The selected quality mode affects the processing speed to large extent. Be pre- pared for very long processing times if the “Best (very slow)” option is used. About the DIRAC processing options: Option Description Auto / Preview This automatically selects the best time/frequency trade-off for real- time/preview performance. This is the fastest setting but might not provide optimal results in all cases. Time localization ++ (instruments, voices)Selects full time localization. This is a good setting for single instru- ments and solo voices. Time localization + Time/frequency localization with the emphasis on time localization. If the previous mode produces echo artefacts, try this option. Average Time/ Frequency localizationThis sets the time/frequency localization halfway between the time and frequency domains. It is the best setting for all general purpose signals. Frequency localization +Time/frequency localization with the emphasis on frequency localiza- tion. Good setting for classical music. Frequency localization ++ (complex mixes)Highest possible frequency localization. This setting might not work well on material with many sharp attack transients, but it can produce good results with less transient/percussive material.